Typical exposure apparatuses used to manufacture devices such as a semiconductor device include a step & repeat exposure apparatus (also called a stepper) which projects, through a projection optical system, the pattern of a master (reticle or mask) onto a plurality of exposure regions on a substrate and sequentially transfers the pattern onto the plurality of exposure regions while stepping the substrate (e.g., a wafer or glass substrate) and a step & scan exposure apparatus (also called a scanner) which repeats step movement and scanning exposure to sequentially transfer the pattern of a master onto a plurality of exposure regions on a substrate. Among these exposure apparatuses, the step & scan exposure apparatus uses only a light component, of exposure light, relatively close to the optical axis of the projection optical system by restricting the exposure light through a slit. Accordingly, the scanner enables higher-precision exposure of a fine pattern with a larger field angle.
These exposure apparatuses have a stage apparatus or driving apparatus (wafer stage or reticle stage) which moves a wafer and reticle at high speed and aligns them. When a stage is driven in such an exposure apparatus, the acceleration/deceleration of the stage entails generation of the reaction force of an inertial force. Transmission of this reaction force to a stage surface plate causes vibrations of the stage surface plate. Such vibrations induce natural vibrations in the mechanism of the exposure apparatus, and high-frequency vibrations occur. This may interfere with high-speed, high-precision alignment.
To solve the above-described problems that pertain to a reaction force, several proposals have been made. For example, an apparatus described in Japanese Patent Laid-Open No. 5-77126 adopts a system in which the stator of a linear motor for driving a stage is supported on a floor independently of a stage surface plate, thereby avoiding vibrations of the stage surface plate due to a reaction force. An apparatus described in Japanese Patent Laid-Open No. 5-121294 adopts a system in which an actuator applies a compensation force, which is equivalent to a reaction force generated upon stage driving, to a force generated in the horizontal direction for a machine frame which supports a wafer stage and projection lens, thereby reducing vibrations of the apparatus due to the reaction force.
Though in any of the above conventional apparatuses, swings of a stage apparatus itself can be reduced, a reaction force generated upon stage driving is transmitted to a floor directly or through a member substantially integrated with the floor. This vibrates the floor, which in turn causes devices placed around an exposure apparatus to vibrate and may adversely affect them. Generally, the floor on which an exposure apparatus is placed has a natural frequency of 20 to 40 Hz. When natural vibrations are induced as the exposure apparatus operates, an adverse effect on the peripheral devices increases.
These days, stage acceleration is increasing along with an increase in processing speed (throughput). For example, in a step & scan exposure apparatus, the maximum acceleration of a stage reaches 4G for a reticle stage or 1G for a wafer stage. In addition, the mass of a stage increases along with an increase in size of a reticle and substrate. For this reason, a driving force defined by <mass of moving member>×<acceleration> becomes very large, and its reaction force becomes enormous. As such a reaction force increases, vibrations of an installation floor due to the reaction force have become non-negligible.
Moreover, the sizes of apparatuses noticeably increase, and an increase in footprint in a manufacturing factory, on which a large number of manufacturing apparatuses are to be placed, is becoming evident as a problem. More specifically, if vibrations transmitted from some apparatuses to the floor are strong, the distances between the apparatuses need to be increased to prevent the other apparatuses from being affected by the vibrations. Consequently, the area virtually occupied by the apparatuses becomes large.
In consideration of the above-described background, the present application considers that a method of using a stator as a reaction force counter which receives a driving reaction force from a movable portion is effective in a driving apparatus which drives the movable portion by an electromagnetic actuator comprising a movable element and the stator.